This invention relates to switched digital communications networks for transporting data traffic between end points via paths multiplexed unto physical or logical links interconnecting switching elements in the network architecture and more particularly to the use of dual, bandwidth related booking factors, one for assigning effective bandwidth values to the initial provisioning and the second for path re-routing in the event of a link failure.
Packet and cell switching networks such as Frame Relay (FR) and Asynchronous Transfer Mode (ATM) are employed extensively in high speed, broadband applications such as voice, video and data transmissions. In packet and cell switching networks, particularly networks delivering real time, variable rate traffic such as voice and video, factors relating to the burstiness of data in paths or logical links imply that the provisioning of paths may use statistical multiplexing gains. Statistical multiplexing gain is using a physical link for provisioning a number of paths whose aggregate peak rate is greater than the bandwidth of the given physical link. In other words, the probability of all paths carrying traffic at peak cell rate (PCR) for ATM or excess information rate (EIR) for frame relay at the same time is low. This implies that the effective bandwidth of a physical or logical link can be different from the actual bandwidth of these links.
The effective bandwidth of the physical or logical links is arbitrarily calculated using a user supplied number called the booking factor (BF) for these links. The effective bandwidth (EBW) for the purpose of provisioning is calculated as the product of the booking factor and the bandwidth of the associated physical or logical linkxe2x80x94link bandwidth (LBW).
For the sake of link redundancy, networks typically make provisions for the availability of multiple possible links for a path to choose from. This allows for the re-route of a path from a failed link to an alternate link between switching elements. To avoid loss of data traffic, however, the alternate route must have sufficient available bandwidth to carry traffic from the failed link as well as the traffic previously assigned to it.
There is, accordingly, a need to provide a system and method for optimizing utilization of bandwidth on a link carrying multi-path traffic while insuring adequate bandwidth on the link for redundancy purposes.
It is an object of the present invention to provide a system and a method for assigning both provisioning and re-routing bandwidth to either a logical or a physical link carrying multi-path data traffic.
According to the invention the provisioning and re-routing bandwidth is based on dual, user selected, booking factors, one for provisioning and one for re-routing.
Therefore in accordance with a first aspect of the invention there is provided in a switched digital communications network having a plurality of network switching elements for multiplexing multiple data paths over links connecting the switching elements, a method of ensuring redundant paths for the data comprising: assigning a first bandwidth booking factor to each link for provisioning traffic; assigning a second bandwidth booking factor to each link for re-routing traffic; and providing a re-route pending flag (RPF) for marking each affected path in the event of a link failure wherein the first booking factor is employed in the absence of a RPF and said second booking factor is employed while a RPF is present.
In accordance with a second aspect of the invention there is provided in a switched digital communications network having a network management system and a plurality of network elements for multiplexing data paths over links interconnecting the elements, a system for optimizing shared use of the links by the switching elements while providing redundancy in the event of failure of one of the links, the system comprising: provisioning means for assigning a first booking factor for use in calculating an effective bandwidth for provisioning the links; re-routing means for assigning a second booking factor for use in calculating an effective bandwidth for the links for use in re-routing data traffic in the event of a link failure; detection means for detecting a link failure and reporting the failure to the network management system; a re-route pending flag for marking each path affected by a link failure; and means to apply the second booking factor to the system upon detection of the re-route pending flag.